Image forming apparatus

ABSTRACT

Provided is an image forming apparatus, including: a manual feed tray on which a recording material is stacked; a first detecting unit; a second detecting unit arranged on an upstream side of the first detecting unit; a third detecting unit arranged on an upstream side of the second detecting unit; a fourth detecting unit detecting a length of the recording material; a display portion; and a control portion determining a size of the recording material based on detection results and causing the display portion to display a first screen displaying the determined size, wherein the control portion causes the display portion to display a second screen for designating the size, when, among the first to third detecting units, a detecting unit located on a downstream side does not detect presence of the recording material and another detecting unit located on an upstream side of the detecting unit, detects the presence.

This application is a Continuation of U.S. application Ser. No.14/857,013, filed Sep. 17, 2015, which claims the benefit of JapanesePatent Application No. 2014-207387, filed Oct. 8, 2014, which are herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an image forming apparatus configuredto form an image on a fed sheet.

Description of the Related Art

Hitherto, an image forming apparatus such as a copying machine or aprinter includes a sheet feeding cassette in an apparatus main body sothat copying or printing can be carried out for a sheet continuously. Asize and a type of the sheet to be used greatly depend on an environmentin which a user uses the image forming apparatus. To address such arequirement, the image forming apparatus is provided with a plurality ofsheet feeding cassettes. Even when the image forming apparatus includesa plurality of sheet feeding cassettes, there may arise a demand toexecute the copying or printing for a sheet different from the sheet seton each of the sheet feeding cassettes. On the assumption that there mayarise such a demand, the image forming apparatus is configured asfollows. Specifically, the image forming apparatus also includes amanual feed tray besides the sheet feeding cassettes so that a desiredsheet can be set with ease.

In order to feed and convey the sheet set on the manual feed tray andform an image in an appropriate position, the size of the sheet needs tobe known, and it is necessary for the user to input the size of thesheet through an operation portion. In this case, each time the usersets a sheet on the manual feed tray, the user needs to set the sheetsize through the operation portion, and hence there has been a fear fora decrease in usability. In contrast, there has been proposed such aconfiguration that a plurality of sensors is arranged on the manual feedtray in a direction of conveying the sheet (Japanese Patent ApplicationLaid-Open No. 2004-231410). A length of the sheet placed on the manualfeed tray in the conveyance direction is detected by the plurality ofsensors. Based on a value acquired from a volume sensor mounted to amovable guide on the manual feed tray, a length of the sheet in adirection orthogonal to the conveyance direction is detected. Based onthe detection results, the image forming apparatus automatically detectsthe sheet size. In the image forming apparatus configured toautomatically detect the sheet size, in order to further enhanceoperability of the user, the sheet size is determined without displayinga screen for checking the automatically detected sheet size on theoperation portion.

The related-art image forming apparatus has the following problems. Whena sensor arranged in the conveyance direction of the sheet fails, and asheet to be subjected to copying or printing is set on the manual feedtray, the sheet size of the sheet set on the manual feed tray iserroneously detected. For example, a sensor arranged in the conveyancedirection of the sheet for detecting a sheet having the size of an A3length (420 mm) may fail and be stuck in an on state. In this case, evenwhen the user sets a sheet having an A4 size (210 mm) on the manual feedtray, the image forming apparatus determines that the sheet size is theA3 length. As a result, the image forming is carried out so as to besuitable for the size of the A3 length. However, the fed sheet is thesheet having the A4 length, and hence the size of a formed image islarger than the size of the fed sheet. As a result, remaining toner thathas not been transferred onto the sheet is adhered to members of animage forming portion, which causes an image failure such as markingback during image forming processing on the subsequent sheet.

The sensor arranged in the conveyance direction of the sheet may failand be stuck in an off state. In this case, even when the user sets asheet having the A3 size on the manual feed tray, the image formingapparatus determines that the sheet size is the A4 length. As a result,the sheet size determined by the image forming apparatus is smaller inlength than the sheet size of the fed sheet in the conveyance direction,and it may be determined that a paper jam occurs.

SUMMARY OF THE INVENTION

The present invention has an object to prevent an image failure or apaper jam caused by an erroneous detection when a sheet size is detectedby a manual feed tray.

In order to solve the above-mentioned problem, one embodiment of thepresent invention includes the following configuration.

There is provided an image forming apparatus, including: a manual feedtray on which a recording material is to be manually stacked; a firstdetecting unit configured to detect presence or absence of the recordingmaterial on the manual feed tray; a second detecting unit arranged on anupstream side of the first detecting unit in a conveyance direction ofthe recording material, the second detecting unit configured to detectpresence or absence of the recording material on the manual feed tray; athird detecting unit arranged on an upstream side of the seconddetecting unit in the conveyance direction, the third detecting unitconfigured to detect presence or absence of the recording material onthe manual feed tray; a fourth detecting unit configured to detect alength of the recording material on the manual feed tray in a directionorthogonal to the conveyance direction; a display portion configured todisplay information; and a control portion configured to determine asize of the recording material based on detection results of the firstdetecting unit, the second detecting unit, the third detecting unit andthe fourth detecting unit, and control portion causing the displayportion to display a first screen displaying the determined size of therecording material, wherein the control portion causes the displayportion to display a second screen for designating the size of therecording material, when, among the first detecting unit, the seconddetecting unit and the third detecting unit, a detecting unit located ona downstream side in the conveyance direction does not detect thepresence of the recording material and another detecting unit located onan upstream side of the detecting unit in the conveyance direction,which does not detect the presence of the recording material, detectsthe presence of the recording material.

According to the one embodiment of the present invention, it is possibleto prevent the image failure or the paper jam caused by the erroneousdetection when the sheet size is detected by the manual feed tray.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system block diagram of an image forming apparatus accordingto a first embodiment and a second embodiment of the present invention.

FIG. 2 is a view for illustrating a configuration of the image formingapparatus according to the first embodiment and the second embodiment.

FIG. 3A is a top view of a manual feed tray according to the firstembodiment and the second embodiment.

FIG. 3B is a graph for showing a relationship between an AD value and asheet size.

FIG. 4A is a diagram for illustrating a manual feed sheet size displayscreen according to the first embodiment.

FIG. 4B is a diagram for illustrating a manual feed sheet sizedesignation screen.

FIG. 5 is a flowchart for displaying the manual feed sheet size displayscreen according to the first embodiment.

FIG. 6 is a flowchart for determining a normal operation of sizedetection according to the first embodiment.

FIG. 7 is a diagram for illustrating a state of a sheet on the manualfeed tray according to the first embodiment.

FIG. 8 is a flowchart for illustrating a display screen switchingoperation according to the first embodiment.

FIG. 9 is a diagram for illustrating a manual feed size detection alarmscreen according to the second embodiment.

FIG. 10 is a flowchart for displaying the manual feed size detectionalarm screen according to the second embodiment.

FIG. 11 is a diagram for illustrating a screen setting screen when amanual feed size is indefinite according to a third embodiment of thepresent invention.

FIG. 12 is a flowchart for displaying a screen setting screen when amanual feed size is indefinite according to the third embodiment.

DESCRIPTION OF THE EMBODIMENTS

Now, embodiments of the present invention are described in detail withreference to the drawings.

First embodiment

(Image Forming Apparatus)

FIG. 1 is a system block diagram of an image forming apparatus accordingto a first embodiment of the present invention, and FIG. 2 is asectional view of an image forming apparatus 100 and a scanner portion101 according to this embodiment. With reference to FIG. 1 and FIG. 2, abasic configuration is described. A control portion 300 illustrated inFIG. 1 includes a CPU 301, a ROM 302, a RAM 303, and an EEPROM 304.When, for example, an instruction (hereinafter referred to as “job”) tostart a printing operation is input to the CPU 301 through a userinterface (UI) of an operation portion 330 (hereinafter referred tosimply as “operation portion 330”), the CPU 301 starts the printingoperation. The CPU 301 can drive and control, via an I/O 307, aconveyance motor 145, a fixing motor 173, a conveyance motor 146, amanual feed conveyance motor 147, a discharge motor 148, and a dischargemotor 149. Further, the CPU 301 can detect, via the I/O 307, an inputsignal input from a conveyance sensor 171, a registration sensor 160, asheet feeding sensor 152, a discharge sensor 195, or a discharge sensor197.

Further, the CPU 301 can detect, via the I/O 307, an input signal inputfrom a manual feed sheet presence sensor 214, a manual feed sheet lengthsensor 218, or a manual feed sheet length sensor 219. The sheet lengthrepresents a length of a sheet in a conveyance direction thereof. TheCPU 301 can detect, via the I/O 307, an input signal input from a manualfeed sheet width sensor 217. In addition, the CPU 301 can also receive ajob input from a network I/F 314 or a facsimile I/F 315. For example,the CPU 301 is connected to a network for communicating to/from anexternal apparatus, and receives a job from the external apparatus viathe network I/F 314. Further, for example, the CPU 301 is connected to atelephone line for receiving FAX, and receives FAX via the facsimile I/F315.

The CPU 301 includes an image processing portion 316 configured toprocess an image corresponding to the job received from the operationportion 330 or the like, and executes image processing such as expansionand rotation of the image. Further, the CPU 301 can control an imageforming portion 320. The image forming portion 320 can control drive andsupply of a high voltage to a process unit 120 indicated by the dottedframe in FIG. 2, a transfer belt 130, a secondary transfer portion 140,and the like, and can control a laser scanner unit 110 indicated by thedotted frame in FIG. 2. Further, the image forming portion 320 cancontrol a temperature of a heater of a fixing device 170 illustrated inFIG. 2. The scanner portion 101 carries out an operation for reading anoriginal when copying is executed. The CPU 301 includes a timer, andcarries out various types of timing control by using the timer tomeasure the time.

With reference to FIG. 1 and FIG. 2, a basic image forming operation isdescribed. When receiving a job from the operation portion 330, the CPU301 analyzes the received job, and starts a printing operation. The CPU301 drives, via the I/O 307, the conveyance motor 145 serving as a drivesource of a cassette pickup roller 151. Thereby, the cassette pickuproller 151 is driven to rotate and sheets within a sheet feedingcassette 150 are fed and conveyed one by one. At this time, the CPU 301uses the sheet feeding sensor 152 to monitor whether or not a sheetfeeding operation has been normally carried out for the sheets.

Sheet conveyance from the manual feed tray 210 is described. The CPU 301operates as follows when receiving an instruction to convey a sheet onthe manual feed tray 210 from the operation portion 330 with the sheetsserving as recording materials being stacked on the manual feed tray210. Specifically, the CPU 301 drives the manual feed conveyance motor147 via the I/O 307 to rotate manual feed pickup rollers 211. Whenrotation of the manual feed pickup rollers 211 is started, the sheets onthe manual feed tray 210 are fed and conveyed one by one. In the samemanner as in the case of sheet feeding from the sheet feeding cassette150, the CPU 301 monitors the registration sensor 160 to determinewhether or not the sheet feeding operation has been normally carriedout. Further, the manual feed sheet presence sensor 214 serving as afirst detecting unit determines whether or not a sheet is set on themanual feed tray 210. A configuration of the manual feed tray 210 isdescribed later in detail.

The CPU 301 causes the process unit 120 to start the image formingoperation so as to be in time with arrival of the sheet at the secondarytransfer portion 140. The process unit 120 includes a photosensitivedrum, a developing device, a charging roller, and a photosensitive drumcleaner. In the process unit 120, after a surface of the photosensitivedrum is charged, an electrostatic latent image is formed on thephotosensitive drum by a laser beam emitted from the laser scanner unit110. The electrostatic latent image formed on the photosensitive drum isdeveloped on the photosensitive drum by the toner within the developingdevice, and becomes a toner image. After that, the toner image formed onthe photosensitive drum is applied with a primary transfer voltage in aprimary transfer portion 121 (illustrated by the dotted frame), and thetoner image is transferred onto the transfer belt 130. The toner imagetransferred onto the transfer belt 130 is conveyed to the secondarytransfer portion 140 by rotation of the transfer belt 130.

Further, the CPU 301 monitors the registration sensor 160 to detect aposition of the sheet conveyed by conveyance rollers 153, conveyancerollers 154, and conveyance rollers 155. Then, in consideration of atiming at which a leading edge of the sheet reaches the registrationsensor 160, the CPU 301 controls the conveyance of the sheet so that theleading edge of the sheet and the leading edge of the toner image on thetransfer belt 130 are aligned with each other at the secondary transferportion 140. For example, when the sheet has reached the registrationsensor 160 earlier than the toner image, the CPU 301 stops the sheet fora predetermined period of time at conveyance rollers 161 and restartsthe conveyance of the sheet thereafter. In the secondary transferportion 140, the CPU 301 applies a secondary transfer voltage to thesheet and the toner image that have reached the secondary transferportion 140, to thereby transfer the toner image onto the sheet.

The sheet having the toner image transferred thereon is conveyed to thefixing device 170 via a conveyor belt 190. In the fixing device 170, theunfixed toner image that has transferred onto the sheet is heated andfixed to the sheet. After that, the sheet is further conveyed to adownstream-side part in the conveyance direction of the sheet. When theleading edge of the sheet subjected to the fixing reaches the conveyancesensor 171, the CPU 301 carries out the following operation.Specifically, the CPU 301 determines, based on contents of the jobdesignated through the operation portion 330 in advance, whichconveyance path of a sheet conveyance path 230, a sheet conveyance path231, and a sheet conveyance path 234 the sheet is to be conveyed byconveyance rollers 162. The CPU 301 switches a conveyance destination ofthe sheet by switching a conveyance flapper 172 and a conveyance flapper182.

Specifically, when the job designated through the operation portion 330is a double-sided print job, and when the sheet is to be discharged withthe printed surface facing down with respect to a discharge port 200,the CPU 301 switches the conveyance flapper 172 in order to convey thesheet to the sheet conveyance path 230. Further, when the sheet is to bedischarged onto a discharge port 196 or a discharge port 199 at a timeof one-sided printing or double-sided printing, the CPU 301 conveys thesheet to the sheet conveyance path 231 by switching the conveyanceflapper 182. In addition, when the job designated through the operationportion 330 is a discharge instruction with respect to the dischargeport 200, the CPU 301 conveys the sheet to the sheet conveyance path 234by switching the conveyance flapper 172 and the conveyance flapper 182.

The sheet conveyed to the sheet conveyance path 231 is further conveyedto a downstream side in the conveyance direction of the sheet(hereinafter referred to as “downstream side”) by conveyance rollers232. Subsequently, the sheet is conveyed to a sheet conveyance path 181,and conveyed toward the discharge port 196 and the discharge port 199.The sheet conveyed to the sheet conveyance path 181 is conveyed bydischarge rollers 241 and discharge rollers 242 driven by the dischargemotor 148. When the job designated through the operation portion 330 isa discharge instruction with respect to the discharge port 196, the CPU301 conveys the sheet to a conveyance path 193 by switching a flapper183, to thereby discharge the sheet onto the discharge port 196 bydischarge rollers 243. When the job designated through the operationportion 330 is a discharge instruction with respect to the dischargeport 199, the CPU 301 switches the flapper 183 toward a conveyance path184. Subsequently, the CPU 301 conveys the sheet to a conveyance path198 by discharge rollers 244, discharge rollers 245, and dischargerollers 246 that are driven by the discharge motor 149, to therebydischarge the sheet onto the discharge port 199.

When the sheet is discharged onto the discharge port 200 with theprinted surface facing down at the time of carrying out the one-sidedprinting, the CPU 301 conveys the sheet to the sheet conveyance path230. Then, at a timing at which a trailing edge of the sheet passesthrough reversal rollers 163, the rollers such as the reversal rollers163 and double-sided conveyance rollers 164 are driven to reverselyrotate so that the sheet is conveyed toward discharge rollers 180, tothereby the sheet is discharged onto the discharge port 200. Whenperforming the double-sided printing, the sheet is conveyed to the sheetconveyance path 230. Then, the sheet is conveyed to a double-sidedturnover conveyance path 233 by the double-sided conveyance rollers 164,165, 166, 179, and 168. Subsequently, at a timing at which the trailingedge of the sheet passes through the double-sided conveyance rollers179, a double-sided turnover flapper 178 is switched toward double-sidedconveyance rollers 169, and the rollers such as the double-sidedconveyance rollers 168 and 179 are driven to reversely rotate.Subsequently, the sheet is conveyed by the double-sided conveyancerollers 169, 175, 176, and 177, to be passed to the conveyance rollers155. After all the jobs are finished, the CPU 301 displays on theoperation portion 330 that the jobs have been finished.

The operation portion 330 includes an input key group 331 (illustratedby the dotted frame) to be used when a user inputs information, and astart key 332 to be depressed when the image forming operation isstarted. Further, the operation portion 330 includes a stop key 333 tobe depressed when the image forming operation or the like isinterrupted, a display portion 334 serving as a display unit, and asleep button 335. The sleep button 335 of the operation portion 330 isdepressed when shifting to a sleep mode in which the image formingapparatus 100 is in a power saving state to reduce power consumption.Moreover, the sleep button 335 is depressed when the image formingapparatus 100 recovers from the sleep mode. A user setting button 336 isdepressed when a screen for displaying a screen setting screen 1200(refer to FIG. 11) is displayed on the display portion 334. The basicimage forming operation is merely an example, and the present inventionis not limited to the above-mentioned configuration.

(Manual Feed Tray)

FIG. 3A is a top view of the manual feed tray 210, and a main body ofthe image forming apparatus 100 is located on the left side of FIG. 3A.When a bundle of sheets (hereinafter sometimes referred to simply as“sheets”) is set on the manual feed tray 210, the sheets are separatedfrom the bundle of sheets one by one by the manual feed pickup rollers211, to be conveyed. When the sheets are set on the manual feed tray210, the manual feed sheet presence sensor 214 outputs the ON signal. AnON signal is input from the manual feed sheet presence sensor 214 to theCPU 301, and the CPU 301 determines that the sheet is present on themanual feed tray 210. The bundle of sheets set on the manual feed tray210 is sandwiched at both end portions of the bundle of sheets in theconveyance direction of the sheet by side-regulating guides 212 and 213serving as regulating plates. This prevents the sheet from being skewfed and conveyed while the sheet is conveyed by the manual feed pickuprollers 211. By causing the side-regulating guides 212 and 213 to slidein directions indicated by arrows 215 and 216 in FIG. 3A, it is possibleto prevent the sheet from being skew fed even when the sheet having anarbitrary sheet width is set. The sheet width represents the length ofthe sheet in a direction orthogonal to the conveyance direction. Inaddition, the side-regulating guides 212 and 213 are coupled to eachother through the manual feed sheet width sensor 217 serving as a fourthdetecting unit and a link member (not shown). The manual feed sheetwidth sensor 217 outputs a signal (AD value) corresponding to positionsof the side-regulating guides 212 and 213 to the CPU 301 in conjunctionwith operations of the side-regulating guides 212 and 213.

The CPU 301 detects the sheet width based on the signal (AD value) inputfrom the manual feed sheet width sensor 217. The manual feed sheetlength sensor 218 serving as a second detecting unit and the manual feedsheet length sensor 219 serving as a third detecting sensor are, forexample, flag-type sensors, and detect the length of the sheet set onthe manual feed tray 210 (refer to FIG. 7). The sheet length representsthe length of the sheet in the conveyance direction. The flag-typesensors include, for example, flags 218 a and 219 a andphotointerrupters 218 b and 219 b (refer to FIG. 7). When the sheet isstacked on the manual feed tray 210, the sheet abuts against the flag,the flag consequently turns, and the flag brings the photointerrupterinto a light shielding state. For example, in this embodiment, when thephotointerrupter is in the light shielding state, the manual feed sheetlength sensors 218 and 219 output ON signals. When a sheet is notstacked on the manual feed tray 210, the flags do not turn, and theflags do not shield the light, and the photointerrupters are in a lighttransmission state. For example, in this embodiment, when thephotointerrupters are in the light transmission state, the manual feedsheet length sensors 218 and 219 output OFF signals. In this embodiment,the manual feed sheet presence sensor 214 also includes a flag 214 a anda photointerrupter 214 b (refer to FIG. 7), but the manual feed sheetpresence sensor 214 may be a sensor of another type.

(Sheet Size Detection)

With reference to FIG. 3B and Table 1, a method of detecting a size ofthe sheet set on the manual feed tray 210 is described. FIG. 3B is agraph for showing a relationship between the signal (AD value) outputfrom the manual feed sheet width sensor 217 based on the positions ofthe side-regulating guides 212 and 213 and a width of the sheet to bedetected in actuality (paper width). Specifically, in FIG. 3B, thehorizontal axis indicates the AD value (such as 0×3D4) output by themanual feed sheet width sensor 217, while the vertical axis indicatesthe size of the sheet (paper width) (such as A4 width (297 mm)). Themanual feed sheet width sensor 217 is a sensor configured to output,specifically, a 10-bit digital value and to output, substantiallylinearly, output values 0×000 to 0×400 in the hexadecimal format.

As shown in FIG. 3B, the output value 0×320 of the manual feed sheetwidth sensor 217 represents 210 mm as the A4R width, the output value0×384 similarly represents 257 mm as the B4R width, and the output value0×3D4 represents 297 mm as the A4 width. In other words, for example,when the AD value 0×320 is input from the manual feed sheet width sensor217, the CPU 301 determines that the paper width of the sheet set on themanual feed tray 210 is 210 mm. The CPU 301 detects the sheet width fromthe output value (AD value) of the manual feed sheet width sensor 217,and detects the sheet length from the output values of the manual feedsheet length sensors 218 and 219. Then, the CPU 301 refers to Table 1 todetermine the size of the sheet from those detection results.

TABLE 1 Manual Manual Manual feed feed feed sheet sheet sheet Manualpresence length length feed sheet Sheet Sheet sensor sensor sensor widthSize width length 214 218 219 sensor 217 A5 210 148 ON OFF OFF 0x320 ±0x10 B5 257 182 ON OFF OFF 0x384 ± 0x10 A4 297 210 ON OFF OFF 0x3D4 ±0x10 A5R 148 210 ON OFF OFF 0x258 ± 0x10 B5R 182 257 ON ON OFF 0x2E4 ±0x10 A4R 210 297 ON ON OFF 0x320 ± 0x10 B4 257 364 ON ON ON 0x384 ± 0x10A3 297 420 ON ON ON 0x3D4 ± 0x10

Table 1 shows the size of the sheet, the sheet width (mm), and the sheetlength (mm) from the left in this order, and shows the information inwhich the sizes of the sheet are associated with the detection resultsobtained by the respective sensors. In addition, Table 1 shows thedetection result from the manual feed sheet presence sensor 214, thedetection results from the manual feed sheet length sensors 218 and 219,and the detection result from the manual feed sheet width sensor 217.The manual feed sheet width sensor 217 outputs the AD value to the CPU301, and the other sensors output an ON signal or an OFF signal to theCPU 301.

The CPU 301 refers to those detection results from the sensors and Table1, to thereby determine the size of the sheet. In other words, the CPU301 functions as a determination unit configured to determine the sizeof the sheet. For example, it is assumed that the manual feed sheetpresence sensor 214 outputs the ON signal, the manual feed sheet lengthsensor 218 outputs the OFF signal, the manual feed sheet length sensor219 outputs the OFF signal, and the manual feed sheet width sensor 217outputs the AD value 0×320±0×10. In this case, the CPU 301 determinesthat the sheet set on the manual feed tray 210 is an A5-size sheet basedon the detection results from the respective sensors and the informationof Table 1. In the same manner, it is assumed that the manual feed sheetpresence sensor 214 outputs the ON signal, the manual feed sheet lengthsensor 218 outputs the ON signal, the manual feed sheet length sensor219 outputs the OFF signal, and the manual feed sheet width sensor 217outputs the AD value 0×320±0×10. In this case, the CPU 301 determinesthat the sheet set on the manual feed tray 210 is an A4R-size sheet tobe fed by a short edge feed of A4.

As shown in Table 1, even when the output value of the manual feed sheetwidth sensor 217 is the same, it is possible to determine that the sizeis different based on a difference in the detection results from themanual feed sheet length sensors 218 and 219. For example, even when theoutput value of the manual feed sheet width sensor 217 is the same ADvalue 0×320±0×10, the size of the sheet can be distinguished between A5and A4R based on the detection results from the manual feed sheet lengthsensors 218 and 219.

Even when the detection results from the manual feed sheet lengthsensors 218 and 219 are the same, the sheet size is distinguished aslong as the output value of the manual feed sheet width sensor 217 isdifferent. For example, even when the detection results from the manualfeed sheet length sensors 218 and 219 are OFF, the CPU 301 can make thefollowing determination based on the AD value of the manual feed sheetwidth sensor 217. For example, the size of the sheet is determined asA5, B5, A4, and A5R when the AD value of the manual feed sheet widthsensor 217 is 0×320±0×10, 0×384±0×10, 0×3D4±0×10, and 0×258±0×10,respectively.

(Manual Feed Sheet Size Display Screen)

With reference to FIG. 4A and FIG. 4B, a screen displayed on theoperation portion 330 in order to prompt the user to check the sheetsize set on the manual feed tray 210 and designate the sheet size isdescribed. FIG. 4A is a manual feed sheet size display screen 500, whichis a first screen displayed on the display portion 334 of the operationportion 330. The manual feed sheet size display screen 500 of FIG. 4A isdisplayed on the display portion 334 of the operation portion 330 inresponse to a state in which the sheet is set on the manual feed tray210, and the sheet size is determined by the CPU 301. For example, in aprocess of S708 of FIG. 5 or a process of S909 of FIG. 8, the CPU 301displays the manual feed sheet size display screen 500 on the displayportion 334 of the operation portion 330.

Specifically, the CPU 301 determines the size of the sheet set on themanual feed tray 210, and displays the determined size of the sheet onthe display portion 334. In this manner, the display screen 500 promptsthe user to check the size of the sheet set on the manual feed tray 210.Referring to FIG. 5 and FIG. 8, a method of detecting the size of thesheet set on the manual feed tray 210 is described later. When the sizeof the sheet set on the manual feed tray 210 matches a displayed size501 displayed on the manual feed sheet size display screen 500, an OKbutton 503 is depressed. When the size of the sheet set on the manualfeed tray 210 does not match the displayed size 501 displayed on themanual feed sheet size display screen 500, a change button 502 isdepressed.

(Manual Feed Sheet Size Designation Screen)

FIG. 4B is a manual feed sheet size designation screen 600, which is asecond screen displayed on the display portion 334 of the operationportion 330. The manual feed sheet designation screen 600 is displayedon the operation portion 330 when an arbitrary size of the sheet isdesignated by the user. For example, the manual feed sheet sizedesignation screen 600 is displayed when the change button 502 isdepressed on the manual feed sheet size display screen 500 of FIG. 4A.Moreover, when the size of the sheet cannot be determined by therespective sensors of the manual feed tray 210 (S910 of FIG. 8), themanual feed sheet size designation screen 600 is also displayed on theoperation portion 330. When the manual feed sheet size designationscreen 600 is displayed on the display portion 334 of the operationportion 330, the size of the sheet is selected by the user depressingany of the buttons of the size designation buttons 601 (indicated by thebroken-line frame). In FIG. 4B, as an example, the A4 size isdesignated. After the sheet size is selected, the sheet size of thesheet set on the manual feed tray 210 is determined when the userdepresses the OK button 602. The image forming apparatus 100 carries outa subsequent image forming operation based on the sheet size designatedthrough the manual feed sheet size designation screen 600. The sheetsize designated through the sheet size designation screen 600 is stored,for example, in the RAM 303.

(Processing from Setting of Sheet to Displaying of Manual Feed SheetSize Display Screen)

FIG. 5 is a basic flowchart for illustrating processing from setting ofthe sheet on the manual feed tray 210 to displaying of the manual feedsheet size display screen 500 on the operation portion 330. Thisprocessing is generally carried out. In order to compare the generalprocessing of FIG. 5 with the processing of FIG. 8 according to thisembodiment, the general processing of FIG. 5 is first described. In S701(a step is indicated as “S”), the CPU 301 determines whether or not themanual feed sheet presence sensor 214 outputs the ON signal. While theCPU 301 is operating, the CPU 301 always monitors the output (ON or OFF)of the manual feed sheet presence sensor 214, and the same holds truefor FIG. 6 and FIG. 8.

In S701, when the CPU 301 determines that the manual feed sheet presencesensor 214 outputs the OFF signal, the CPU 301 repeats the processing ofS701. In S701, when the CPU 301 determines that the manual feed sheetpresence sensor 214 outputs the ON signal, the processing proceeds toS702. In S702, the CPU 301 stores the output value of the manual feedsheet width sensor 217 as a variable AdVal (AdVal=output value of manualfeed sheet width sensor 217). The variable AdVal is a variable forstoring a value to be stored in the RAM 303. In S703, the CPU 301 storesthe output value of the manual feed sheet length sensor 218 as avariable L1Val (L1Val=output value of manual feed sheet length sensor218). In S704, the CPU 301 stores the output value of the manual feedsheet length sensor 219 as a variable L2Val (L2Val=output value ofmanual feed sheet length sensor 219). Each of L1Val and L2Val is avariable for storing a value to be stored in the RAM 303. In thefollowing description, the variable for storing the value to be storedin the RAM 303 is referred to simply as “variable of the RAM 303”.

In S705, the CPU 301 compares the respective values stored as thevariables in the RAM 303 in the processing of S702 to S704 with Table 1to determine whether or not Table 1 includes a suitable size. When theCPU 301 determines that Table 1 includes a suitable size in S705, theCPU 301 stores information (such as A5) of the suitable size as PapSizeserving as the variable in the RAM 303 (PapSize=suitable size) in S706.When the CPU 301 determines that Table 1 does not include a suitablesize in S705, the CPU 301 stores information (for example, “indefinite”)indicating that the size is indefinite as the variable PapSize(PapSize=indefinite) in S707.

In S708, based on the information of the size of the sheet stored as thevariable PapSize in S706 or S707, the CPU 301 displays the manual feedsheet size display screen 500 on the display portion 334 of theoperation portion 330, and brings the processing to an end. In otherwords, based on the information of the size of the sheet stored as thevariable PapSize in S706 or S707, the manual feed sheet size displayscreen 500 described with reference to FIG. 4A is displayed on thedisplay portion 334 of the operation portion 330. Specifically, the CPU301 displays the information (such as “A4”) of the size of the sheet,which is stored as the variable PapSize in S706, on the displayed size501 of the manual feed sheet size display screen 500. Alternatively, theCPU 301 displays the information (such as “indefinite”) indicating thatthe size of the sheet is indefinite, which is stored as the variablePapSize in S707, on the displayed size 501 of the manual feed sheet sizedisplay screen 500.

(Processing of Determining Whether or Not Detection of Sheet Size byManual Feed Tray is Normal)

FIG. 6 is a flowchart for determining whether or not the processing ofdetecting the size of the sheet set on the manual feed tray 210 can benormally carried out. In this embodiment, when the sheet is set on themanual feed tray 210, the processing illustrated in FIG. 6 is carriedout. In S801, the CPU 301 determines whether or not the manual feedsheet presence sensor 214 outputs the OFF signal. Moreover, the CPU 301resets and starts the timer. In S801, when the CPU 301 determines thatthe manual feed sheet presence sensor 214 outputs the OFF signal, theprocessing proceeds to S802. In S802, the CPU 301 determines whether ornot the manual feed sheet length sensor 218 outputs the ON signal. Whenthe CPU 301 determines that the manual feed sheet length sensor 218outputs the ON signal, the processing proceeds to S804. In S802, whenthe CPU 301 determines that the manual feed sheet presence sensor 218outputs the OFF signal, the processing proceeds to S803. In S803, theCPU 301 determines whether or not the manual feed sheet length sensor219 outputs the ON signal. When the CPU 301 determines that the manualfeed sheet length sensor 218 outputs the ON signal, the processingproceeds to S804. In S803, when the CPU 301 determines that the manualfeed sheet presence sensor 219 outputs the OFF signal, the processingproceeds to S806. In this case, none of the sensors arranged on themanual feed tray 210 in the conveyance direction of the sheet detectsthe presence of the sheet, and the CPU 301 determines that the sizedetection for the sheet is normal.

In S804, by referring to the timer, the CPU 301 determines whether ornot a predetermined period of time T1 has elapsed. When the CPU 301determines that the predetermined period of time T1 has not elapsed, theCPU 301 repeats the processing of S804. In S804, when the CPU 301determines that the predetermined period of time T1 has elapsed, theprocessing proceeds to S805. In S805, the CPU 301 again determineswhether or not the manual feed sheet presence sensor 214 outputs the ONsignal. When the CPU 301 determines that the manual feed sheet presencesensor 214 outputs the ON signal, the processing proceeds to S806. Inthis case, among the sensors arranged on the manual feed tray 210 in theconveyance direction of the sheet, there is no sensor in the OFF stateand arranged on the downstream side in the conveyance direction withrespect to a sensor in the ON state. Therefore, the CPU 301 determinesthat the size detection for the sheet is normal. In S805, when the CPU301 determines that the manual feed sheet presence sensor 214 outputsthe OFF signal, the processing proceeds to S807. In other words, whenthe manual feed sheet presence sensor 214 outputs the OFF signal inS801, and still outputs the OFF signal after the predetermined period oftime T1 has elapsed, the processing proceeds to S807.

In S807, the CPU 301 sets a normally detectable flag of the manual feedsize, which is a variable in the RAM 303, to OFF (the normallydetectable flag of the manual feed size=OFF), and the processing returnsto S801. The CPU 301 determines that the detection of the sheet size bythe sensors arranged on the manual feed tray 210 cannot be normallycarried out. In this state, despite the fact that the manual feed sheetpresence sensor 214 outputs the OFF signal, namely the sheet is not seton the manual feed tray 210, at least one of the manual feed sheetlength sensors 218 and 219 outputs the ON signal. In this case, thesensor arranged on the manual feed tray 210 cannot normally detect thesize of the sheet. In this embodiment, when the sensor located on thedownstream side in the conveyance direction of the sheet does not detectthe presence of the sheet, and the sensor located on the upstream sideof the sensor, which does not detect the presence of the sheet, in theconveyance direction detects the presence of the sheet, the followingoperation is carried out. Specifically, the CPU 301 determines that thesize of the sheet cannot be determined by the plurality of sensorsarranged on the manual feed tray 210.

The reason for the processing of S804 in which the CPU 301 waits untilthe predetermined period of time T1 elapses is described below. There isa conceivable state in which, in the course of the setting of the sheeton the manual feed tray 210 by the user, the manual feed sheet presencesensor 214 outputs the OFF signal, and at least one of the manual feedsheet length sensors 218 and 219 outputs the ON signal. The transientstate of the detection result of the sensors generated in the course ofthe setting of the sheet on the manual feed tray 210 cannot bedetermined as the abnormality of the sensors. Therefore, in S804, theCPU 301 waits until the predetermined period of time T1 elapses. In thisembodiment, the predetermined period of time T1 is, for example, 3seconds.

In S806, the CPU 301 sets the normally detectable flag of the manualfeed size, which is the variable in the RAM 303, to ON (the normallydetectable flag of the manual feed size=ON). This is because the size ofthe sheet can be determined by the plurality of sensors arranged on themanual feed tray 210 when the processing proceeds to S806. In S808, theCPU 301 sets an alarm screen display flag, which is the variable in theRAM 803, to OFF (alarm screen display flag=OFF), and the processingreturns to S801. The alarm screen display flag is described later in asecond embodiment of the present invention.

In S801, when the CPU 301 determines that the manual feed sheet presencesensor 214 outputs the ON signal, the processing proceeds to S809. InS809, the CPU 301 determines whether or not the manual feed sheet lengthsensor 219 outputs the ON signal. In S809, when the CPU 301 determinesthat the manual feed sheet length sensor 219 outputs the OFF signal, theprocessing proceeds to S806. In this way, when the sensor located on thedownstream side in the conveyance direction of the sheet detects thepresence of the sheet, and the sensor located on the upstream side ofthe sensor, which detects the presence of the sheet, in the conveyancedirection of the sheet does not detect the presence of the sheet, theCPU 301 determines that the size detection for the sheet is normal.Moreover, when all of the sensors arranged on the manual feed tray 210in the conveyance direction of the sheet detect the presence of thesheet, the CPU 301 determines that the size detection for the sheet isnormal.

In S809, when the CPU 301 determines that the manual feed sheet presencesensor 219 outputs the ON signal, the processing proceeds to S810. InS810, the CPU 301 determines whether or not the manual feed sheet lengthsensor 218 outputs the ON signal. When the CPU 301 determines that themanual feed sheet length sensor 218 outputs the ON signal, theprocessing proceeds to S806. In S810, when the CPU 301 determines thatthe manual feed sheet length sensor 218 outputs the OFF signal, theprocessing proceeds to S811. In this case, as described with referenceto FIG. 3A, among the respective sensors arranged on the manual feedtray 210, the manual feed sheet presence sensor 214 and the manual feedsheet length sensor 219 arranged on the both sides of the manual feedtray 210 in the conveyance direction output the ON signals. The manualfeed sheet length sensor 218 arranged on the center side of the manualfeed tray 210 in the conveyance direction outputs the OFF signal.

In S811, by referring to the timer, the CPU 301 determines whether ornot a predetermined period of time T2 has elapsed. When the CPU 301determines that the predetermined period of time T2 has not elapsed, theprocessing of S811 is repeated. In S811, when the CPU 301 determinesthat the predetermined period of time T2 has elapsed, the processingproceeds to S812. The CPU 301 again determines whether or not the manualfeed sheet length sensor 218 outputs the ON signal. In S812, when theCPU 301 determines that the manual feed sheet length sensor 218 outputsthe ON signal, the processing proceeds to S806. When the CPU 301determines that the manual feed sheet length sensor 218 outputs the OFFsignal, the processing proceeds to S807. The predetermined period oftime T2 in S811 is 3 seconds, which is the same as the predeterminedperiod of time T1. The predetermined period of time T2 is set to asufficient period of time for resolving a deflection on a sheet A, evenif the deflection is generated when the sheet A is stacked on the manualfeed tray 210. FIG. 7 illustrates a state in which the deflection isgenerated on the sheet A when the sheet A is stacked on the manual feedtray 210, and a portion near the center of the sheet A in the conveyancedirection is temporality lifted upward from the manual feed tray 210.

The processing of S809 to S812 are carried out in order to detect thefollowing state of the sheet on the manual feed tray 210. FIG. 7 is anenlarged view of a portion of the manual feed tray 210 of the imageforming apparatus 100 illustrated in FIG. 2. As illustrated in FIG. 7,the portion near the center of the sheet A set on the manual feed tray210 may be in the lifted state due to stiffness or the deflection (alsoreferred to as “curl”) of the sheet. In the state illustrated in FIG. 7,the flag 214 a blocks the light in the photointerrupter 214 b, and themanual feed sheet presence sensor 214 is thus turned on. The flag 218 adoes not block the light in the photointerrupter 218 b, and thus themanual feed sheet length sensor 218 outputs the OFF signal. Further, theflag 219 a blocks the light in the photointerrupter 219 b, and thus themanual feed sheet length sensor 219 outputs the ON signal. In the stateillustrated in FIG. 7, the sheet size of the sheet A on the manual feedtray 210 cannot be normally detected. Even if the sheet itself isnormally set on the manual feed tray 210, when the manual feed sheetlength sensor 218 is defective, and is always outputs the OFF signal,the size of the sheet set on the manual feed tray 210 cannot be normallydetected. Even in this state, a case may occur in which the manual feedpaper presence sensor 214 outputs the ON signal, the manual feed sheetlength sensor 218 outputs the OFF signal, and the manual feed sheetlength sensor 219 outputs the ON signal. The control illustrated in FIG.6 is carried out independently of and in parallel with other control.

(Presence or Absence of Normal Detection of Sheet Size)

FIG. 8 is a flowchart for illustrating the processing of carrying outdisplay on the operation portion 330, which is based on the flowchart ofFIG. 5. In this processing, based on the result of the determination asto whether or not the size detection for the sheet can be normallycarried out by using the sensors arranged on the manual feed tray 210 inthe processing illustrated in FIG. 6, the display is carried out on theoperation portion 330. In this embodiment, in place of the basicflowchart of FIG. 5, the processing may also be carried out by followingthe flowchart of FIG. 8. In S901, the CPU 301 determines whether or notthe manual feed sheet presence sensor 214 outputs the ON signal. Whenthe CPU 301 determines that the manual feed sheet presence sensor 214outputs the OFF signal, the processing of S901 is repeated. In S901,when the CPU 301 determines that the manual feed sheet presence sensor214 outputs the ON signal, the CPU 301 determines whether or not thenormally detectable flag of the manual feed size, which is the variableof the RAM 303, is set to ON in S902. The normally detectable flag ofthe manual feed size holds the value set by the processing of S806 orS807 of FIG. 6.

In S902, when the CPU 301 determines that the normally detectable flagof the manual feed size is set to ON, the processing proceeds to S903.The CPU 301 refers to the value of the normally detectable flag of themanual feed size, and determines that the size detection for the sheetcan be normally carried out by using the sensors arranged on the manualfeed tray 210. The CPU 301 carries out the size detection for the sheeton the manual feed tray 210 by the processing starting from S903. Theprocessing from S903 to S909 of FIG. 8 is the same as the processingfrom S702 to S708 of the FIG. 5 described above, and description thereofis omitted. When the CPU 301 normally carries out the size detection forthe sheet by using the sensors arranged on the manual feed tray 210, theCPU 301 displays the manual feed sheet size display screen 500 of FIG.4A on the display portion 334 of the operation portion 330 in S909.

In S902, when the CPU 301 determines that the normally detectable flagof the manual feed size is set to OFF, the CPU 301 determines that thesize detection for the sheet cannot be normally carried out by using thesensors arranged on the manual feed tray 210. Therefore, the CPU 301displays the manual feed sheet size designation screen 600 describedwith reference to FIG. 4B on the display portion 334 of the operationportion 330 in S910. This screen is used to prompt the user to designatethe size of the sheet instead of automatically determining the size ofthe sheet when the size detection for the sheet cannot be normallycarried out by using the sensors arranged on the manual feed tray 210.

In this embodiment, the screen to be displayed on the display portion334 of the operation portion 330 is switched between for a case in whichthe size detection for the sheet can be normally carried out by usingthe sensors arranged on the manual feed tray 210 and for the case inwhich the size detection cannot be normally carried out. In other words,when the size detection for the sheet can be normally carried out, theCPU 301 displays the manual feed sheet size display screen 500 of FIG.4A on the display portion 334 by the processing of S909 of FIG. 8. Whenthe size detection for the sheet cannot be normally carried out, the CPU301 displays the manual feed sheet size designation screen 600 of FIG.4B on the display portion 334 by the processing of S910 of FIG. 8. As aresult, according to this embodiment, without spoiling the usability,the image failure or the paper jam caused by the erroneous detection ofthe sheet size on the manual feed tray 210 can be prevented.

As described above, according to the first embodiment, the image failureor the paper jam caused by the erroneous detection when the sheet sizeis detected by the manual feed tray can be prevented.

Second embodiment

(Manual Feed Size Detection Alarm Screen)

Referring to FIG. 9 and FIG. 10, the second embodiment is now described.FIG. 9 illustrates a screen for prompting the user to check temporaryplacement and the like. This screen is displayed when it is determinedthat the size detection for the sheet on the manual feed tray 210 cannotbe normally carried out in the processing described with reference toFIG. 6. In this embodiment, the following cases are assumed as the casein which the size detection for the sheet cannot be normally carried outby the sensors arranged on the manual feed tray 210. A first case is acase in which at least one of the manual feed sheet length sensor 218and the manual feed sheet length sensor 219 fails. A second case is acase in which a sheet other than the sheet subjected to the printing oran object (hereinafter referred to as “foreign matter”) is temporarilyplaced on the manual feed tray 210. The temporary placement refers toplacement of a sheet not to be subjected to copying or printing or anobject that changes the state of the sensor arranged in the conveyancedirection of the sheet. FIG. 9 illustrates a manual feed size detectionalarm screen 1000 which is a third screen, when assuming the secondcase. Specifically, the temporary placement of a foreign matter on themanual feed tray 210 is assumed, and a screen for prompting the user tocheck the manual feed tray 210 is displayed. The user removes theforeign matter on the manual feed tray 210, and the sheet is set again.Then, the size detection for the sheet is again carried out by thevarious sensors arranged on the manual feed tray 210. The user candepress the OK button 1001 to return the display on the display portion334 of the operation portion 330 from the display of the manual feedsize detection alarm screen 1000 to a predetermined display screen.

(Display of Manual Feed Size Detection Alarm Screen)

FIG. 10 is a flowchart for illustrating processing for carrying out thedisplay of the manual feed size detection alarm screen 1000. Theprocessing from S1101 to S1110 of FIG. 10 is the same as the processingfrom S901 to S910 of the FIG. 8 described above, and description thereofis omitted. In S1102, when the CPU 301 determines that the normallydetectable flag of the manual feed size is set to OFF, the processingproceeds to S1111. The CPU 301 determines that the detection of thesheet size by the sensors arranged on the manual feed tray 210 cannot benormally carried out. In S1111, the CPU 301 determines whether or notthe value of the alarm screen display flag stored by the processing ofS808 of FIG. 6 is set to ON.

In S1111, when the CPU 301 determines that the alarm screen display flagis set to OFF, the processing proceeds to S1112. The case, in which thenormally detectable flag of the manual feed size is set to OFF and thealarm screen display flag is set to OFF, corresponds to a statedescribed below. In the state, the size detection cannot be normallycarried out for the first time after the size detection has beennormally carried out by using the sensors arranged on the manual feedtray 210, and this state is a first abnormality detection. In S1112, theCPU 301 displays the manual feed size detection alarm screen 1000described with reference to FIG. 9 on the display portion 334 of theoperation portion 330. In S1113, the CPU 301 sets the alarm screendisplay flag, which is the variable of the RAM 303, to ON, and theprocessing proceeds to S1114. In the processing of S1113, the CPU 301stores the fact that the manual size detection alarm screen 1000 is oncedisplayed on the display portion 334. In S1114, the CPU 301 determineswhether or not the manual feed sheet presence sensor 214 outputs the OFFsignal. When the CPU 301 determines that the manual feed sheet presencesensor 214 does not output the OFF signal, the CPU 301 repeats theprocessing of S1114. In S1114, when the CPU 301 determines that themanual feed sheet presence sensor 214 outputs the OFF signal, namely,the sheet has been removed from the manual feed tray 210, the processingreturns to S1101.

In S1111, when the CPU 301 determines that the alarm screen display flagis set to ON, the CPU 301 determines that, after the size detectioncould not normally be carried out, the manual feed size detection alarmscreen 1000 has once been displayed on the operation portion 330. TheCPU 301 does not display the manual feed size detection alarm screen1000 on the display portion 334, and the processing proceeds to S1110.In this embodiment, when the CPU 301 determines that the size of thesheet cannot be normally detected by using the sensors arranged on themanual feed tray 210, the CPU 301 only once displays the manual sizedetection alarm screen 1000 on the display portion 334.

Only when the alarm screen display flag is set to OFF by the processingof S808 of FIG. 6, the CPU 301 carries out the following processing.Specifically, after the CPU 301 determines that the size detection canbe normally carried out, or after the three sensors arranged on themanual feed tray 210 can no longer detect the sheet, when the CPU 301determines that the size detection is abnormal for the first time, theCPU 301 displays the manual feed size detection alarm screen 1000 on theoperation portion 330. As a result, when a foreign matter is temporarilyplaced on the manual feed tray 210, the CPU 301 appropriately promptsthe user to check the manual feed tray 210. Then, the size detection forthe sheet can be normally carried out. In a case in which at least oneof the manual feed sheet length sensor 218 and the manual feed sheetlength sensor 219 fails, the display of the manual feed size detectionalarm screen 1000 is not repeated. As a result, the usability isprevented from being spoiled.

As described above, according to the second embodiment, the imagefailure or the paper jam caused by the erroneous detection when thesheet size is detected by the manual feed tray can be prevented.

Third embodiment

(Selection of Screen)

Referring to FIG. 11 and FIG. 12, a third embodiment of the presentinvention is now described. FIG. illustrates a screen displayed on thedisplay portion 334 when the sheet size is determined to be indefiniteafter the size detection for the sheet is carried out by the sensorsarranged on the manual feed tray 210. The screen of FIG. 11 is displayedwhen the CPU 301 determines that the sheet size is indefinite. Thisscreen functions as a selecting unit configured to select, in advance,which of the manual feed sheet size display screen 500 and the manualfeed sheet size designation screen 600 is to be displayed on the displayportion 334 of the operation portion 330. A screen setting screen 1200for selecting, in advance, the screen displayed when the sheet size onthe manual feed tray 210 is indefinite includes two selection buttons.Specifically, the screen setting screen 1200 includes a selection button1201 for selecting the manual feed sheet size display screen 500 and aselection button 1202 for selecting the manual feed sheet sizedesignation screen 600. The user depresses any one of the selectionbuttons 1201 and 1202, to thereby select any one of the screens to bedisplayed in advance. After any one of the selection buttons 1201 and1202 is depressed, an OK button 1203 on the screen setting screen 1200when the sheet size on the manual feed tray 210 is indefinite isdepressed. As a result, which of the screens is to be displayed isdetermined. This screen setting screen 1200 is displayed in response tothe depression of the user setting button 336 on the operation portion330.

(Processing when Sheet Size on Manual Feed Tray is Indefinite)

FIG. 12 is a flowchart for illustrating processing for carrying out thedisplay switching. This processing is carried out by following thescreen selected on the screen setting screen 1200 when the sheet size isdetermined to be indefinite in the size detection for the sheet by thesensors arranged on the manual feed tray 210. The processing from S1301to S1308 of FIG. 12 is the same as the processing from S901 to S908 ofthe FIG. 8 described above, and description thereof is omitted. InS1308, the CPU 301 stores information (such as “indefinite”)representing that the sheet size is indefinite as PapSize which is thevariable in the RAM 303. The CPU 301 determines which of the settings ofthe screen is made in advance (S1310). The setting is made on the screensetting screen 1200 when the sheet size on the manual feed tray 210 isdetermined to be indefinite, which is illustrated in FIG. 11.

The CPU 301 determines the content to be displayed on the operationportion 330 according to the setting made in advance. The setting ismade on the screen setting screen 1200 when the sheet size on the manualfeed tray 210 is determined to be indefinite. When the manual feed sheetsize display screen 500 is set on the screen setting screen 1200 (YES inS1310), the processing proceeds to S1309.

When the manual feed sheet size designation screen 600 is set on thescreen setting screen 1200 (NO in S1310), the processing proceeds toS1311. In S1309, the CPU 301 displays the manual feed sheet size displayscreen 500 of FIG. 4A on the display portion 334 of the operationportion 330 based on the sheet size stored as the PapSize, which is thevariable in the RAM 303, and finishes the processing. In S1311, the CPU301 displays the manual feed sheet size designation screen 600 of FIG.4B on the display portion 334 of the operation portion 330, and finishesthe processing. Information of the sheet size designated on the manualfeed sheet size designation screen 600 of FIG. 4B is stored in an area,for example, in the RAM 303, different from the area for the detectionresults (S1303 to S1305) obtained by the sensors arranged on the manualfeed tray 210. The information of the designated sheet size stored inthe RAM 303 or the like is maintained until the sheet size is designatedon the manual feed sheet size designation screen 600 next time.

In the first and second embodiments, when the size of the sheet on themanual feed tray 210 is indefinite, the manual feed sheet size displayscreen 500 is displayed (S908 and S909 of FIGS. 8, and S1108 and S1109of FIG. 10). In this embodiment, the setting is made in advance on thescreen setting screen 1200 of FIG. 11. When the size of the sheet on themanual feed tray 210 is determined to be indefinite, according to themade setting, any one of the manual feed sheet size display screen 500and the manual feed sheet size designation screen 600 is displayed. As aresult, according to this embodiment, the usability can be increased.

As described above, according to the third embodiment, the image failureor the paper jam caused by the erroneous detection when the sheet sizeis detected by the manual feed tray can be prevented.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

What is claimed is:
 1. An image forming apparatus comprising: a manualfeed tray on which recording material is to be manually stacked; a firstdetector configured to detect a presence or absence of the recordingmaterial on the manual feed tray; a second detector arranged on anupstream side of the first detector in a conveyance direction of therecording material, the second detector configured to detect a presenceor absence of the recording material on the manual feed tray; a thirddetector arranged on an upstream side of the second detector in theconveyance direction of the recording material, the third detectorconfigured to detect a presence or absence of the recording material onthe manual feed tray; a display portion configured to displayinformation; and a controller configured to determine a size of therecording material based on detection results of the first detector, thesecond detector and the third detector, and to cause the display portionto display the determined size of the recording material, wherein thecontroller is further configured to cause the display portion to displaya message representing that the size of the recording material has notbeen detected in a case that, among the first detector, the seconddetector and the third detector, a detection result of a downstream-sidedetector located on a downstream side in the conveyance direction doesnot represent the presence of the recording material and a detectionresult of an upstream-side detector located on an upstream side of thedownstream-side detector with respect to the conveyance directionrepresents the presence of the recording material.
 2. The image formingapparatus according to claim 1, wherein the controller is furtherconfigured to cause the display portion to display the message in a casethat detection results of the first detector and the third detectorrepresent the presence of the recording material and a detection resultof the second detector does not represent the presence of the recordingmaterial.
 3. The image forming apparatus according to claim 1, whereinthe controller is further configured to cause the display portion todisplay the message in a case that a detection result of the firstdetector does not represent the presence of the recording material and adetection result of the second detector represents the presence of therecording material.
 4. The image forming apparatus according to claim 1,wherein the controller is further configured to cause the displayportion to display another message for prompting to check the recordingmaterial on the manual feed tray along with the message.
 5. The imageforming apparatus according to claim 1, wherein the controller isfurther configured to cause the display portion to display thedetermined size of the recording material in a case that detectionresults of all of the first detector, the second detector and the thirddetector represent the presence of the recording material.
 6. The imageforming apparatus according to claim 1, wherein the controller isfurther configured to cause the display portion to display thedetermined size of the recording material in a case that, amongdetection results of the first detector, the second detector and thethird detector, a detection result of a downstream-side detector locatedon a downstream side in the conveyance direction represents the presenceof the recording material and a detection result of an upstream-sidedetector located on an upstream side of the downstream-side detectorwith respect to the conveyance direction does not represent the presenceof the recording material.
 7. The image forming apparatus according toclaim 6, further comprising a fourth detector configured to detect alength of the recording material on the manual feed tray in a directionorthogonal to the conveyance direction, wherein the controller isconfigured to determine the size of the recording material based on thedetection results of the first detector, the second detector, the thirddetector, and the fourth detector.
 8. The image forming apparatusaccording to claim 7, wherein: the manual feed tray has regulatingplates configured to regulate both end portions of the recordingmaterial in the direction orthogonal to the conveyance direction, andthe fourth detector is configured to output a value corresponding topositions of the regulating plates in conjunction with an operation ofthe regulating plates.